Multiple-tooth broach



Dec. 21, 1954 w. J. --PHANEUF 2,697,271 MULTIPLE TOOTH BR OACH Filed May 12, 1954 2 Sheets-Sheet l INVENTOR. 5B WILROSE 3. PHANEUF MM PM Dec. 21, 1954 w. J. PHANEUF 2,697,271

MULTIPLE-TOOTH BROACH Filed May 12, 1954 2 Sheets-Sheet 2 INVENTOR. WILROSE J. PHANEUF.

AT TY MULTIPLE-TOOTH BROACH Will'ose J. Phaneuf, Hudson, Mass., assignor to The Lapointe Machine Tool Company, Hudson, Mass., a corporation of Maine Application May 12, 1954, Serial No. 429,295 4 Claims. (Cl. 23-951) This invention relates to multiple-tooth broaches as used for broaching slots or openings of special cross section. The broach shown herein is designed for cutting the so-called Christmas tree grooves which receive the butts of the rotor blades in certain commercial turbines.

Broaches of this type are quite expensive, and with continued operation they become worn to such an extent that they will not cut to full size and are therefore no longer usable.

It is the general object of this invention to provide special sizing members which may be assembled with a multiple-tooth breach in such manner that they will follow-up the regular broach and will cut or shave the slots or openings to full or standard size.

A further object is to provide such sizing members in consecutive sections, each of which may be oppositely offset when necessary to accurately maintain full cutting width over a long period of use.

The invention further relates to arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims.

A preferred form of the invention is shown in the drawings, in which Fig. 1 is a plan view of a pair of the improved sizing members;

Fig. 2 is a side elevation thereof;

Fig. 3 is an end view, looking in the direction of arrow 3 in Fig. 2;

Fig. 4 is a plan view showing a pair of sizing members assembled in a multiple-tooth broach; and

Fig. 5 is a side view, looking in the direction of arrow 5 in Fig. 4.

Referring particularly to Figs. 4 and 5, a multipletooth broach is shown which comprises a series of separate broaching members assembled in a longitudinally extended bar having a groove or channel 11. The successive broaching members are longitudinally aligned, and are held from displacement by blocks or abutments 12 seated in transverse recesses in the bar 10.

In the use of this type of broach, the slots or openings in each workpiece are commonly roughed-out in any convenient manner, and the broach itself performs a final forming and finishing operation only and does not actually remove any very considerable amount of stock.

In Figs. 4 and 5, the leading broach member 20 comprises a block having a plurality of pilot teeth which enter the previously roughed-out slots or openings in advance of the cutting teeth. The next or roughing member 22 is provided with breaching teeth which gradually approach full size, and successive broach members, as 24 and 25, provide for chamfering, finishing and topping the slots or recesses.

Such a broach is fully shown and described in my prior United States Patent No. 2,585,832 issued February 12, 1952.

So lon as the broach thus far described operates satisfactorily and cuts to full size, the special sizing members to be next described are not required, but as soon as the broach begins to out under size, these special sizing members 30 and 31 are to be placed in the groove 11 of the bar 10 to follow the regular broaching members and abutting one of the holding blocks 12.

Referring particularly to Figs. 1 to 3, the sizing members 30 and 31 are preferably constructed in pairs as elongated bars.

Each member 30 is provided with cutting units 40 each of which is provided with cutting teeth 41 and with a United States Patent 0 blank or non-cutting surface 42. Each member 31 is correspondingly provided with cutting units 50 each having cutting teeth 51 and a blank or non-cutting surface 52.

Each member 30 or 31 also has a V-shaped longitudinal recess 44 (Fig. 3) to receive a clamping bar 45 secured by screws 46.

After the blank portions 42 and 52 of the cutting units 40 and 50 have been ground off or relieved, the cutting teeth 41 and 51 are formed and finished. The members 30 and 31 are then separated as indicated at 33. A pair of them may then be placed in a grooved bar 10 in abutting relationship with each other and also abutting one of the blocks 12 in said bar 10.

The sizing members 30 and 31 are then secured in position by tightening the screws 46, and the teeth 41 and 51 will then supplement the work done by the regular broach, thus prolonging the usefulness thereof.

Eventually, the teeth 41 and 51 may themselves become worn, in which case the member 30 may be lightly ground off along its side surface 60 adjacent its teeth 41, and a thin shim 62 may be inserted alongside the member 31.

When the clamping bars 45 are then tightened, the sizing member 30 will have its ground surface 60 forced against the adjacent side wall of the groove 11 in the bar 10. The member 31 will be oppositely offset an equal amount by the shim 62. This will have the effect of spreading the sizing members and restoring full size of the slots produced thereby.

The grinding operation on the sizing member 30 may be repeated as necessary for a considerable number of times, and shims of increasing thickness may be provided. The useful life of the original broach is thus very substantially prolonged.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim is:

1. A combination broach comprising a bar having a longitudinal groove to receive regular breaching members, a pair of sizing members mounted in said groove of said bar to follow said regular members, means to prevent longitudinal displacement of said sizing members, each of said sizing members having a plurality of cutting units with cutting teeth at one side only of the center plane of the broach and the cutting teeth in the two sizing members being on opposite sides of said plane, and holding means engaging that surface of one sizing member which is more remote from the cutting teeth.

2. A combination broach as set forth in claim 1, in which the holding means presses the sizing member against that side wall of said groove which abuts the cutting side of said member.

3. In a broach having an elongated bar with a longitudinal groove in one face thereof, in combination, a pair of sizing members each having a body portion insertable in said groove and said members being longitudinally adjacent in said groove, each member having a plurality of cutting units with cutting teeth on one side of each unit and with a blank edge on the opposite side and with the cutting teeth in said two members on opposite sides of the longitudinal center line, and clamping means engaging each member and forcing the body portion of said member against a side wall of the groove in said bar.

4. A combination broach comprising a bar having a longitudinal groove to receive regular broaching members, a pair of sizing members mounted in said groove of said bar to follow said regular members, means to prevent longitudinal displacement of said sizing members, each of said sizing members having a plurality of cutting units with cutting teeth at one side and blank edges at the other side, the cutting teeth in the two sizing members being on opposite sides of the longitudinal center line of said broach, and holding means engaging each sizing member and forcing said member transversely against the same side wall of said groove in said bar, and a thin spacing shim interposed between that side of one member having blank edges and the adjacent side wall of said groove.

No references cited. 

